Condenser.



H. P. DONLE. CONDENSER.

APPLICATlON FILED JAN.29.I93'1`.

1,240,958. .Patented Sept. 25, 1917.

2 SHEETSf-SHEET l.

H. P. DGNLE.

CONDENSER.

APPLICATION FILEDr JAN29| 19H.

Patented Spt. 25, 1917.

2 SHEETS-SHEET 2.

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' .L 34' 35 L l 37 3l im ff I l i ZHTC/a UNITED srairas arianna ernten.

HAROLD P. DONLE, OF BELMONT, MASSACHUSETTS, SSIGNOR TO CONNECTICUT TELEPHONE &; ELECTRIC COMPANY, OF MERIDEN, CONNECTICUT, A CORPORA- TION OF CONNECTICUT.

CONDENSER.

Patented Sept. 25, 191'?.

Application filed January 29, 1917. Serial No. 145,070.

To all whom t may concern:

Be it known that I, HAROLD l). DoNLn, a citizen of the United States of America, residing atelmont, Massachusetts, have invented a new and useful Condenser, of which thefollowingis a specification.

My invention relates 'to' condensers of variable capacity and aims to provide a condenser of this character which will be relatively small and compact, simple and inexpensive as to construction and which will be capable of relativelyJ fine adjustment and therefore particularly adapted for radio telegraphy. Another object of the invention is to provide a condenser which while compact in form willbe of relatively great capacity and which when brought' to thel adjusted condition will remain in that condition until further adjustments are desired.

A. further object is to so construct the device that its action 'will be constant and not subject to changes such as would result from the wearing down of the dielectric by frictional engagement of the condenser plates therewith.

In-the progress of the art ofradio telegraphy various types of condensers have been developed, they being. an essential part of both the receiving and transmitting equipment.

rllhe potentials in the transmitting circuit are usually` high and condensers for this portion ofthe apparatus have therefore been developed mostly to avoid leakage and hysteresis losses.

Condensers for the receiving apparatus on the other hand have received less attention even though they are an important part of the equipment, as evidenced by the fact that in some systems live or more condensers are employed in each receiving set.

A typefof variable capacity which has come into more or less general use is what is known as the rotary condenser, consisting essentially of two sets of semieircular metal plates separated by washers, one set being mounted on a shaft which rotates through an angle of one'hundred and eighty degrees so that the plates thereon will intermesh with the other relatively fixed set of plates. The capacity of this condenser is almost directly proportional to the movement of the rotary plates and the instrument while fairly satisfactory possesses certain serious defects. For one thing the percentage variation in capacity is small for it is impossible to adjust with any degree of accuracy below a certain point on the scale (ftcen degrees). Also as air is the usual dielectric in this instrument a small capacity occupies considerable space. Further the rotating plates tend to throw the shaft supportingthem out of balance so that a slight jar or movement is sufficient ordi.- narily to destroy the adjustment, this bei coming quite a serious defect on shipboard.

rThese and other disadvantages have been .overcome and the objects set forth above have been accomplished in the present invention by employing a pair of condenser plates, one of which is covered with a thin layer of mica' or like dielectric material, the capacity being varied by the adjustment of the plates with respect to each other. special feature is the shifting of the plates in a direct or non-rotating path toward each other so as to avoid a rubbing engagement of the plates with the interposed mica or similar dielectric.

Other features of the invention are the mounting of the condenser plates within a hollow supporting base and the provision of indicating means for showing the approximate condition or relation of the condenser plates. `Further features will become apparent as the specification proceedsN In the accompanying drawings I have illustrated my invention embodied in prae- .tical and preferred forms but l would have it understood that changes and modifica* tions may be resorted to without departure from the real spirit and scope of the invention.

In said drawings:

Figure l is a plan view of the invention embodied in a compact and practical form for radio work.

Fig. 2 is a view in side elevation.

Fig. 3 is a cross sectional view taken substantially on the plane of the line 3 3 of Fig. l, showing the condenser plates in a partially separated condition.

is a similar view with less parts appearing in section and showing the condenser plates brought together.

Fig. 5 is a bottom plan view of the de-I vice with the -bottom cover removed.

Fig. 6 is a detail sectional view of one of the binding posts showing the iiexible connection therefrom to the movable condenser plate, this view being `taken substantially on the plane of the line 6 6 of Fig. 1.

Fig. 7l is a cross' sectional view of a Y slightly modified form of the invention.

Fig. 8, is a bottom plan view of the main portions of this device.

Fig.v 9 is a diagrammatic view showing curves plotted Vfrom some of the results ob- `tained with the device.

In the first form illustrated a metallic supporting base 10 is provided, the same being generallyhollow in form to constitute a casing for certain of the parts and being furthermore formed on the under surface of the top thereof as a plate or condenser element 11. The second condenser plate isV designated 12 and is shown as housed within the'hollow base opposite the first condenser surface 11 and supported on a movable head 13 carried by the stud 14,

said second condenserjplate being insulated from its support by a block of suitable *invhandhold 20, said operating nger hold having a collar portion 21 sleeved down over the nut and adjustably secured on-the nut by aclamping screw 22.` .This Vconstruction enables a variable or adjustablefconnection of the operating member with the nut.

A spring is'shownprovided at 23 encircling j the screw stud 14 and operating against the underside ofv thel base at its upper end and against the supporting lhead 13 at its lower end, it thus exerts its ten- `sion to shift the lower plate away from the upper plate and thus separatelthe condenser plates when allowed to do soby the unscrew.

ing of the control nut. ,p y

A layer of suitlble dielectric,v material is interposed between4 the condenser plates, mica having been found a .desirable vmaterial for this purpose and this dielectric which I have indicated at 24 may be secured directly to the face of one;l of the condenser plates, it being shown secured to the face of the upper condenser' plate in the illustration. The mica may beheld in place on the face of the condenser plate by suitablel lacquer.

To aid 1n To prevent attrition or Wearing down of the l,dielectric and consequent variation in theI operation of the device I provide means for guiding the relatively movable condenser platevso as to prevent a rubbing engagement `with the dielectric, said means comprising', in the illustration, outstanding guiding studs 25 dependent from the underside of thetop ofthe base and fitting in slots 26 formed, in the first form of the invention illustrated', in the edge of the member' 13- carrying the movable lcondenser plate. y

The guide studs in this first form are 'shown setvin the insulation 27, but this is unnecessary where, as in this case, the condenser plate 12 is insulated from the head 13 which supports it.

The supporting base may be formed with a suitable outstanding base flange 28 forl securing the condenser in position and 'the open bottom of the base may b e closed by a suitablebottom cover 29. j ,Suitable terminals are provided br the cuitwires, said terminals being here illustrated as binding posts 30 and 31, the first 'of' these being suitably insulatedfrom the metallicsupporting base as by mounting it in an insulating block as indicated at 32 in Fig. 6 and the second binding post makes di- -reet electrical contact with the condenser plate portion of the base as indicated in Fig. 3. Connection is made from theinsulated binding post to the movable condenser plate by a suitable flexible connection such as a Wire 33 as shown in Figs. 5 and 6.

From the foregoing it will be apparent' that by means of the screw connection de- -scribed the plates may be readily adjusted with respect to eachother and with the interposed dielectric4 and it furthermore will be evident that by reason of the direct and nonrotating movement of one plate .toward the other there will be no Vrubbin contact with the dielectric and consequent y no Wearing down or displacement of' the dielectric. It

v.will furthermore be evident that slow or rapid adjustments may be made at will and that the adjustments may be brought down to 'av very fine point. Another important 4feature of my ,invention is that the adjustments are permanent in that the device will remain in the condition in which it has been,

, set, jarring and rolling motions' having no` disturbing effect upon the adjustments.

the attainment of the proper adjustments I'have provided the-device with indicatin means taking the Aform of a scale 34 provi ed on the .top of the supporting i base and an index` or pointer 35 carried by 4the operatitng member and registering on said-scale;A 3 This Scale may be calibrated in units of capacity or the like or may be simply marked off in arbitrary divisions as shown in the illustration. At opposite ends .graduations `trom to NW indicate ot the scale stops 36-37 may be provided to prevent over-running the scalej said stops being engaged, in the present instance7 by the outstanding pointer 35.

The detachable connection or the linger liold illustrated enables' said finger hold being removed While making the preliminary adjustment ot the condenser plates. Urdinarily this preliminary7 adjustment simply consists in turning the operating nut up tar enough to bring the condenser plates into close engagement. T he operating linger hold is then applied'ivith the pointer thereof in position engaging the final stop 37 (the right hand stop in case of a right hand screw suoli as' that indicated). The operating 4member may then be turned to separate the plates, the indicating pointer in such operation travelingbackover the scale to the point of maximum separation ot' the plates.- It the initial adjustment has been inaccurate or is unsatisfactory the handle may at any time be readily removed and new adjustment made. j

rilhe constructionillustrated in 7 and 8 is similar in general respects to that already described` the main distinction being that in this latter toi-m the hollow base l0.

is made ot insulating material and it theretore becomes necessary to apply a separate metallic condenser plate ll to the underside ot the base lor cooperation ivith the movable condenser plate 12, the second condenser plate. in this case, being slioivn secured directly tothe operating screiv ivithout 'the intermediacy oit any insulation.` lin this construction also the ymovable condenser plate is guided in a straight path inte engagement iviththe other condenser plate by vforming the guiding` .slots QG directly in the peripheral portion thereoiC to .receive the guide studs Also in this construction the Firstbindiiig post P is con nected tvitlithe movable condenser plate by vflexible connection 33 and the second binduros on the condenser Tale and 'he graduatious indicate capacity in in' ads. rlhc solid black line indi ot au actual test using an aun ot thirty-sixY threads to the inch. ot control and the ease ot au.' be apparent troni this curve. line indicates the calculated mica ot approximately tive teu t inch thickiicss as the dielectric and-dash line indicates calculated in Without the mica. The dash line indicates results using an adjusting screw ot sixty- :tour Ythreads to the inch.

The capacity ot the condenser Without the inica. neglecting edge etl'lect, would be inversely proportional to the separation olI the plates. lilith the one plate however covered With mica, which material has a dielectric constant or approximately six times that oit air, (the capacity increasing directly With the dielectric constant), the capacity would be inversely proportional to d-FA: Where M equals thickness of the mica, K equals dielectric constant of mica and A equals the distance from the outer surface of the mica to the other plate.

lFroi'n the shape of the curve of the actual test (the solid line) it will be apparent that this type of condenser is of special value for use in a Wave-meter7 in audion wing-circuits. .liloreover the size ot the device makes it particularly useful for small portable receiving sets.

ilfliat l claim is:

l. j, condenser comprising a support having a condenser surface thereon and provided ivith 1iassage therethrough7 a second condenser member iter cooperation with the lirst condenser member provided with a screw .stud extendingv treely through the passage in the iii-st condenser member, an interposed dielectric between the condenser members, cooperating guides on the support and 'the second condenser i einher tor guiding the second condenser ir mber in a straight path toward amL aivay from the first condenser member. a spring tor separating the condenser members and a imt engaging the screw stud flor drav-.ing ae second condenser niember teivard "lie iirst condenser member.

com iser comprising a support iriv- "rre` a condeY i 'tace thereon, a second condenser roil cooperation With the iii-st member. a scrciv stud con; i rwoud condenser memberD s id screw stud for oper*- iii't the second condense n respect to the lirst coi'ideziser ineinl .'erposed dielectric between c ndczif .'einbers, a linger hold e'ugagi :j turna f tue same and means iger hold in adjustable a hollow sup- `enser suri'faec at not. a mov hollov.T .i i ri on ai t neen the c 'z ri` tei-posed oethe movrfov ively sta ti on z i v ing the the sta ti one p lll@ condenser member n .opposition to the sprmg, and' means for guldmg the movable Condenser member non-rotatably 1n lts movements toward and away from labe rst 0011-'A i denser member.

4. A condenser comprising a metallic base havmg an mtegral surface formed to con: stltute a condenser member, a second condenser member mounted on the base and insulated from the first condenser member, an interposed dielectric between the condenser members and means for shifting the Second condenser member toward and away from the integral Condenser surface of the metallie supporting base.

' HAROLD P. DONLE. 

